Force limited power actuated device

ABSTRACT

An electrified overhead, carrier-type material handling system including a power-propelled, hoist-style carrier comprising an electric motor driven cable-type load hoist, the cable of which is suspended in part by a flexible resilient closed vessel filled with liquid connected to fluid pressure responsive switch in the hoist motor circuit for preventing operation of the hoist motor upon the existence of a load on the hoist in excess of a predetermined amount.

United States Patent June 17, 1975 Pamer FORCE LIMITED POWER ACTUATED 3,153,391 10/1964 Forestall 104/152 3.223.385 12/1965 Murakami 254/173 R DEVICE [75] Inventor: Karl A. Pamer, Chagrin Falls, Ohio [73] Assignee: McNeil Corporation, Akron, Ohio [22] Filed: June 25, 1973 [21] App]. No.: 374,669

[52] US. Cl 254/173 B [51] Int. Cl. B66d 1/48 [58] Field of Search 187/28; 254/173 B, 172; 212/11 [56] References Cited UNITED STATES PATENTS 2,109,297 2/1938 McMurry et al. 254/173 B 2,274,339 2/1942 Loomis 254/173 B 2,609,l8l 9/1952 Jaeschke 254/173 B X 2,923,379 2/l960 Stelzer 187/28 X Primary Examiner-Robert B. Reeves Assistant ExaminerCharles A. Marmor Attorney, Agent, or F irm-Watts, Hoffman, Fisher & Heinke Co.

[ 5 7 ABSTRACT An electrified overhead, carrier-type material handling system including a power-propelled, hoist-style carrier comprising an electric motor driven cable-type load hoist, the cable of which is suspended in part by a flexible resilient closed vessel filled with liquid connected to fluid pressure responsive switch in the hoist motor circuit for preventing operation of thehoist motor upon the existence of 'a load on the hoist in excess of a predetermined amount.

2 Claims, 2 Drawing Figures FORCE LIMITED POWER ACTUATED DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to power actuated devices comprising controls for preventing operation thereof when overloaded.

2. Description of the Prior Art Power actuated devices comprising controls for preventing operation when overloaded are known but the controls are expensive, unreliable or lack the ruggedness and sensitivity required for many applications.

SUMMARY OF THE INVENTION The invention provides a novel and improved power actuated device comprising control for preventing operation of the power mechanism under overload conditions.

The invention more specifically provides a motor driven device such as, an electric motor driven, cable type hoist, comprising a flexible resilient elastomer vessel filled with fluid the pressure of which is a function of the load on the motor and which prevents operation of the motor when the fluid pressure exceeds a predetermined amount.

The invention resides in certain constructions and combinations and arrangements of parts and further objects and advantages thereof will be apparent to those skilled in the art to which it relates from the following description of preferred embodiment thereof described with reference to the accompanying drawings forming a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a section of an electrified, overhead, monorail carrier system, including a power-propelled carrier comprising an electric motor driven hoist, embodying the present invention; and

FIG. 2 is an enlarged view of a portion of FIG. 1 with parts omitted and other parts in section on the vertical centerline of the left-hand hoist cable reach and parallel to the axis of rotation of the hoise cable drum.

DESCRIPTION OF THE PREFERRED EMBODIMENT While the invention is susceptible of embodiments in many devices it is herein shown as embodied in an electric motor propelled hoist-type carrier of an overhead material handling system.

Referring to the drawings, the overhead, monorail, material handling system A comprises a monorail having lower, horizontal flange portions 11 upon which a movable carrier C is supported by spaced pairs of flanged wheels 12 for movement along the rail from one location to another by an electric motor 13. The carrier C is provided with a load bar 14 suspended between the two sets of wheels 12 for dependingly supporting an electric motor driven hoist H which includes an electric motor for rotating the cable drum 21 to which a load grab in the form of a hook block G is con nected by a cable 22. The cable drum 21 is rotatably supported in the frame 23 of the hoist H and connected to the motor 20 in a conventional manner. The power for the motors 13,20 is supplied from longitudinal conductor bars 24,25,26 mounted alongside the rail 10 by brackets 28. In the system illustrated, the motors are of the three-phase alternating current type and, therefore, three conductor bars are provided. The power'for the electric motors is transferred from the conductor bars to the carrier C by current collector s 30, mounted on the carrier C and in engagement with the conductor bars 24,25,26. The operation of'the'motors 13,20 is controlled from a pendant control station P suspended from the carrier C by a flexible conduit.

The travel motor 13 is operated liy.:stop push button switch 42, a forward push button switch 45 and a reverse push button switch 46 all on the pendant control station P, and two limit switches 50,51 mounted on the carrier C and actuated in sequence as the carrier moves along the rail by a cam or trip 52 carried by the rail. Actuation of the switches 50,51 by the cam or trip 52 stops the carrier.

The hoist motor 20 is operated by two push button switches 60,61 and an on-off automatic" selector switch 62 on the pendant control station P. The hoist motor 20 is automatically activated to lower the load grab G when the carrier is stopped by the cam or trip 52 with the automatic selector switch 62 in its on position. The push button'switches 60,61 when depressed manually cause up and down travel or movement, respectively, of the load grab G.

The overhead carrier system thus far described is similar to that disclosed in Forestall US. Pat. No. 3,153,391, entitled Overhead Carrier-Type Material Handling System to which reference is made for a more complete description thereof.

One end of the cable 22 is connected to the cable drum 21. The other end is fixed to a clevis which in turn is connected to an eye-bolt 71 by a bolt 72. The upper end of the eye-bolt 71 extends through the central opening of a disk-like member 75 and has jamb nuts 76,77 threaded ontoits upper end for preventing movement of the bolt 71 thorugh the member 75 in a downwardly direction. The member 75 has a lower panel surface which rests on the upper part of an elastic, flexible, hollow, ring-like member filled with liquid 82. The member 80 rests upon an upwardly facing abutment surface 81 of a cup-shaped member 83 the bottom of which engages and is supported on a bracket 84 secured to the frame 23 of the hoist H. The bottom side of the member 83 and the bracket 84 have apertures therein through which the shank of the eye-bolt extends with clearance therebetween. The upwardly extending annular flange of the member 83 projects above the top side of the member 80 and the lower part of the member 75. There is a small clearance between the member 75 and the flange of the member 83. The member 80 is connected by a conduit to a pressure responsive switch 92 in the circuit for the hoist motor 20. The switch 92 is normally closed but when a load is lifted by the grab G the member 80 is compressed forcing fluid therein to the fluid actuated switch 92 and if the pressure of the fluid 82 in the member 80 and the conduit 90 reaches a predetermined amount the switch 92 will open to prevent operation of the hoist motor 20.

From the foregoing description of the preferred embodiment of the present invention it will be apparent that there has been provided a novel and improved power-actuated device, such as the preferred embodiment shown, that is, an elastic-driven hoist comprising inexpensive controls, sensitive and reliable in operation, rugged in construction and essentially maintenance free for preventing operation of a poweractuated device under overload conditions.

Having thus described my invention, 1 claim:

1. In a motor-driven hoist, a frame, having an upwardly facing abutment surface, a cable drum rotatably supported by said frame, an electric motor supported by said frame and connected to said cable drum for rotating said cable drum, a resilient flexible closed toroidal shaped elastomer vessel filled with fluid supported on said abutment surface, a member supported on the upper side of said closed vessel, cable means having one end connected to said cable drum and its other end connected to said member supported on the upper side nected to said vessel and responsive to fluid pressure in said vessel in excess of a predetermined amount for preventing operation of said motor.

2. A motor-driven hoist, as claimed in claim 1 in which the said elastomer vessel has a central opening through which extends the said other end of said cable means connected thereto. 

1. In a motor-driven hoist, a frame, having an upwardly facing abutment surface, a cable drum rotatably supported by said frame, an electric motor supported by said frame and connected to said cable drum for rotating said cable drum, a resilient flexible closed toroidal shaped elastomer vEssel filled with fluid supported on said abutment surface, a member supported on the upper side of said closed vessel, cable means having one end connected to said cable drum and its other end connected to said member supported on the upper side of said closed vessel, a load grab connected to said cable means, and an electric control circuit for selectively operating said motor, said control circuit including a normally closed pressure responsive switch connected to said vessel and responsive to fluid pressure in said vessel in excess of a predetermined amount for preventing operation of said motor.
 2. A motor-driven hoist, as claimed in claim 1 in which the said elastomer vessel has a central opening through which extends the said other end of said cable means connected thereto. 